Coated, especially painted, metal strip has become popular in many industrial sectors. Particularly the fact that metal strip can be stored in a simple manner wound as coil and pre-coated unwound directly from the coil before shaping makes it interesting for many applications.
Meanwhile, methods and installations, which use electromagnetic radiators for drying and/or cross-linking the coating of the metal strip, in particular infrared radiators, are known from DE 101 58 008 A1 for example. Such infrared radiators need cooling, which can be effected by means of a liquid, but also by means of a cooling gas, in particular cooling air, which absorbs the waste heat from the radiation sources.
In such a drying unit the infrared radiation is substantially converted to heat in the coating, whereby the solvent is expelled from the coating within a short time and/or cross-linking of the coating takes place.
The solvent released in the inner chamber of the drying unit must be removed from the latter. For this purpose gas, preferably air, which has previously been brought to a temperature above the condensation temperature of the solvent, is conducted into the inner chamber. This gas absorbs the solvent; both are extracted from the latter at another place in said inner chamber.
Such a drying unit thus has a gas or air supply, wherein overall large volumes of gas are needed, which must be conditioned, more particularly heated, with relatively high consumption of energy.
Conditioned generally means that the gas is treated to meet given requirements within specific parameters such as purity, humidity and temperature, for example.
The present invention is directed to resolving these and other matters.